Thread guide unit for circular knitting machines

ABSTRACT

THIS DISCLOSURE RELATES TO A THREAD GUIDE UNIT FOR RAPIDLY REPLACING ONE THREAD WITH ANOTHER BEFORE COMMENCING THE ROWS OF KNITTING, SAID UNIT COMPRISING A DRUM OSCILLATING ABOUT ITS OWN AXIS AND PROVIDED WITH PERIPHERAL GROOVES EXTENDING PARALLEL TO SAID AXIS, SAID GROOVES BEING ARRANGED TO HOUSE THREAD GUIDE MEMBERS, A STEP CAM FAST WITH SAID DRUM, A FIRST SLIDE MEMBER FOR CAUSING THE LOWERING OF ONE OF SAID THREAD GUIDE MEMBERS, A SEC-   OND SLIDE MEMBER ARRANGED TO ENGAGE SAID STEP CAM AND LOCK SAID DRUM, A SERIES OF CONTROL MEMBERS EQUAL IN NUMVER TO THE NUMBER OF STEPS OF SAID STEP CAM, EACH OF SAID CONTROL MEMBERS BEING ARRANGED TO ENGAGE A CORRESPONDING STEP OF SAID CAM AND CAUSE THE ROTATION OF SAID DRUM.

Dec. 7, 1971 F. PIANA ETAI- 3,625,027

THREAD GUIDE UNIT FOR CIRCULAR KNITTING MACHINES Filed April 14, 1969 5Sheets-Sheet 1 INVENTORS FRANCESCO PIANA BY ANGELO BREGA Dec. 7, 1971 F.PIA NA ETAL 3,625,027

THREAD GUIDE UNIT FOR CIRCULAR KNITTING MACHINES Filed April 14, 1969 5Sheets-Sheet 2 lNVENTOR-S FRANCESCO PIANA ANGELO BREGA PIANA ETAL3,625,027

THREAD GUIDE UNIT FOR CIRCULAR KNITTING MACHINES Dec. 7, 1971 5Sheets-Sheet 5 Filed April 14, 1969 Dec. 7, 1971 PlANA ETAL 3,625,027

THREAD GUIDE UNIT FOR CIRCULAR KNITTING MACHINES Filed April 14, 1969 5Sheets-Sheet 4 INVENTORS FRANCESCO PIANA ANGELO BREGA AGENT THREAD GUIDEUNIT FOR CIRCULAR KNIT'QIIYG MACHINES Filed April 14, 1959 v F. PIANAE'rAL '5 Sheets-Sheet 5 United States Patent O 9,2 Int. Cl. D04]: 9/06,15/58 US. Cl. 66-19 6 Claims ABSTRACT OF THE DISCLOSURE This disclosurerelates to a thread guide unit for rapidly replacing one thread withanother before commencing the rows of knitting, said unit comprising adrum oscillating about its own axis and provided with peripheral groovesextending parallel to said axis, said grooves being arranged to housethread guide members, a step cam fast with said drum, a first slidemember for causing the lowering of one of said thread guide members, asecond slide member arranged to engage said step cam and lock saiddr-um, a series of control members equal in number to the number ofsteps of said step cam, each of said control members being arranged toengage a corresponding step of said cam and cause the rotation of saiddrum.

BACKGROUND OF THE INVENTION The present invention relates to a threadguide unit for a circular kniting machine.

In circular knitting machines, comprising a fixed framework and arotating equipment, and fed with a plurality of threads by an equalnumber of bobbins or reels, it is necessary to be able to replace onethread with another promptly and with precision, before starting theformation of rows of stitches of the knitted fabric. It is known, infact, that in circular knitting machines, at each rotation of therotating equipment with respect to the fixed framework, there occurs theformation of many new rows of knitting with threads coming from the feedunit and supplied by respective thread guides (which are equal in numberto the feed units). After the completion of a certain number of rowswith a given type of thread (for example with a given color) it isnecessary, without interrupting the work rhythm of the machine, toreplace the thread used until that moment with a new thread, for exampleof different color, in order to effect one or more successive rows ofthe knitting. Since the operative speed of circular knitting machinescan reach high values and since it is necessary to successively feed theknitting with numerous different threads, it is clear that it isnecessary to provide a thread guide distributor unit of rationalconception which is such as to guarantee a sure working in allconditions of use.

SUMMARY OF THE INVENTION The thread guide unit according to theinvention is designed to guarantee a precise feeding of the threads tothe zone of the machine in which the formation of the knitwear takesplace and to guarantee that the passage of the feeding of one thread tothat of the feeding of another thread, at the moment in which a suitablecontrol is given by the programmer unit, occurs rapidly and withoutuncertainties in the selection of the thread among the many available orin its positioning in the work zone.

Another object of the present invention is that of providing a threadguide unit for circular knitting machines which is of simple and sturdystructure and comprises a limited number of moving parts, so that theinertias in play during the rapid operations which lead to the re-3,625,027 Patented Dec. 7, 1971 placement of the thread feeding themachine are as small as possible.

These and other objects which will better appear hereinafter areachieved by a thread guide unit for circular knitting machines formed bytwo parts, of which one part constitutes the fixed framework and theother part constitutes the mobile equipment, and in which fast with oneof said parts there is a plurality of bobbins for feeding the threadguide unit with a plurality of threads, while the other of said partscarries the members for the formation at each turn of the rotatingequipment of the successive rows of knitting; said thread guide unitbeing characterized in that it is associated to one of said parts andcomprises: a drum member oscillating about its own axis against theaction of spring means, and provided with parallel grooves or guidesalong its generatrixes, said guides being designed to slidably houserespective thread guides fed by said bobbins and provided with a ridgeradial to said drum, the ridges of all the thread guides being arrangedto follow one another along at least a co-axial circumferential arc ofsaid drum; a step cam circumscribing the drum for an are at least equalto said co-axial circumferential arc and fast with said drum, said stepcam defining steps which are at least equal in number to the number ofthread guides; a first slidable slide member co-operating with springmeans and arranged inside a guide which is fixed with respect to saiddrum and parallel to the axis of said drum, said slide member beingarranged to engage, during its downward movement, the ridge of theadjacent thread guide in order to cause the lowering of the latter alongthe respective guide and arrange the thread guide in the work position;a raising member fast with said slide member and designed to engage theridge of the thread guide which is in the work position so as to cause,during the upward movement of said slide, the raising of said threadguide from the lowered work position; a second slidable slide memberco-operating with spring means and arranged in a guide which is fixedwith respect to said drum and which extends parallel to the axis of saiddrum, said second slide member being arranged to engage the steps ofsaid step cam and lock the drum in the angular position in which one ofthe steps is locked by said second slide member; on the other part ofthe said circular knitting machine there being provided superposed firstcontrol members, equal in number to the number of steps of said cam andarranged to engage a respective step due to the rotation of said firstor second part of the machine; second control members in phaserelationship with said first control members and equal in number to thesteps of said cam, said second control members being arranged to causethe disengagement of said second slide member from the step cam; andmeans arranged to engage said first slide member and cause the raisingand lowering thereof in phase relationship with said first and secondcontrol members.

BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantageswill appear more clearly from the detailed description of a preferred,but not exclusive, embodiment of a thread guide unit according to theinvention, in its application to a circular knitting machine of the kindin which the rotation equipment carries all the members which govern thefeeding of the thread, while the fixed framework carries the members forthe formation, at each turn of the rotating equipment, of the successiverows of knitting (needles and the like).

There is particularly considered a machine designed to form an opentubular fabric, that is a fabric which is made by knitting along only anarc of the circumference of the machine, so that each row of stitchesbegins at a generatrix of the needle cylinder of the machine andterminates at another generatrix thereof at a distance from said firstgeneratrix equal to said arc. Machines which manufacture open tubularfabric are known, e.g. from the British Patent No. 1,000,387.

In the accompanying drawings which relate to the application of thethread guide unit to the machine of the described type:

FIG. 1 is a. perspective view of the complete thread guide unit in restposition;

FIG. 2 is an exploded view of some of the main members of the same unit;

FIG. 3 is a frontal view of the unit with a thread guide in the workposition;

FIG. 4 is a partially sectioned view of the connection between therevolving drum which carries the thread guides and the fixed cover orcowling;

FIG. 5 is a cross-section of the drum which carries the thread guides;

FIG. 6 is a longitudinal section of the unit in the situation in whichone thread guide is in work position;

FIG. 7 is a section similar to the preceding one when none of the threadguides are in the work position;

FIG. 8 is a plan view from below of the thread guide unit;

FIGS. 9, and 12 show cross-sectional views, similar to that of FIG. 5 ofthe sequence of the phases which lead to the substitution in the workposition of two thread guides which follow one another in anti-clockwisedirection on the drum;

FIGS. 11 and 13 show the same sequence seen frontally;

FIGS. 14, and 16 show, in front view, the sequence of the phases whichlead to the substitution, in the work position, of two thread guideswhich follow one another in clockwise direction on the drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to said figures,on the rotating equipment of the machine there is provided a pluralityof thread guide units arranged along its periphery. Only one of theseunits will be considerd. Each of said units is fed by any number ofyarns coming from respective reels. In the illustrated embodiment thethread guide unit is fed by five yarns indicated at 1 which mayinditferently be single or double yarns.

The thread guide unit is contained inside a cover or hood 2 fixed to therotating equipment and internally hollow.

In the front portion of the hood member 2 projecting towards the outsideof the rotating unit there is provided a front vertical milling 3designed to act as a guide and a vertical through groove 4 which is alsodesigned to act as a guide as will be seen hereinafter. In the upperportion of the hood 2 there is also provided a through hole whichcommunicates with the interior of the chamber defined by the hood.Inside the hood 2 there is arranged an oscillating drum 5 which ispivoted at its top to the hood by means of the pin 6. Between the drum 5and the fixed hood there is interposed a torsion spring 6a which tendsto maintain the drum in a rest position which, in the illustratedembodiment, is achieved with an anticlock-wise rotation of the drum. Onthe lateral surface of the drum 5 there are provided parallel grooves.or guides 7 which extend along generatrixes of the drum and are equal innumber to the threads 1 (besides a further guide, as will be seenhereinafter). Said guides 7 extend along only an arc of the drumsurface. Inside each of said guides 7 there is arranged a verticallymovable thread guide 8 which is provided at its upper end with a lug 9which extends outwardly and radially to the drum.

In the upper portion of the drum 5, adjacent each of the thread guidesthere are secured pairs of resilient 4 springs 9a which are spreadable.These springs 9a are designed to retain each thread guide in the raisedrest position by acting as pincers which are inserted in grooves 911provided on the two sides of each thread guide.

Consequently, when a thread guide has to be lowered the initialresistance of the springs 9a is overcome and the springs are forced toopen and reclose on the grooves 911.

In the first guide 4 (which together with the second guide 3 isprotected and closed by a plate 2a) there is guided a rod-like conveyorelement or first slide member 10 for the thread guides. Said element 10is provided on its outside with a pin tooth 11 which projects radiallyfrom the groove 12 of the plate 2a, and is provided on its inside with asnug 12a, and a ring are or raising member 13 which is arranged belowthe snug 12a and is spaced therefrom by a portion slightly greater inheight than the lugs 9 of the thread guides 8. The conveyor 10 isnormally maintained in the lowest or working position of its run alongthe guide 4 by the action of a lever 14 fulcrumed in 15 to the hood 2and loaded by a spring 16. In such manner the lever, with its end roller17, normally urges the upper end of the slide member 10 downwards (FIG.6). The upper position, shown in FIG. 7, corresponds to the restposition of the thread guide. From said rest position the slide member10 is brought into the working position in the manner describedhereinafter.

The vertical stroke of the conveyor 10 is limited to the support whichthe ridge 8a of the thread guide finds with the sector 41 whichsurrounds all the zone of the drum in which the thread guides arearranged. To the lower portion of the cylindrical drum 5 there issecured a step cam member 18 which substantially comprises a pluralityof descending steps 19 which cover the drum for a distance approximatelyequal to the length of the arcuate surface along which the guides 7 ofthe thread guides are arranged. The step cam 18, that is, oscillatesfast with the drum 5. More precisely the step cam 18 is secured to thesector 41 which is secured to the drum 5.

In the second guide 3 there is slidably arranged a second rod-like slidemember 20* which projects downwardly from said guide and engages thesteps 19' of the cam 18. The slide member 20 is provided with a lowerend 24 extending inwardly and radially to the drum 5 and defining ameans for engaging the steps 19 aligned with the trajectory of the slide20 (the maximum stroke of the slide member 20 is limited by the lengthof a slot 21 provided in the plate 2a and in which the pin tooth 22secured to the element 20 slides). The element 20, which is thusdesigned to act as a stop latch for the step cam 18, is maintained urgeddownwards by the compressed spring 23.

Until now the members fast with the rotating equipment of the machineand mobile with respect to the fixed framework have been described.There will now be described the control means acting on the variousparts of the thread guide unit, such means being arranged on said fixedframework.

Such means comprise a certain number of superposed latches which aregenerally indicated at 25. Their number is equal to that of the steps 19of the cam 18. They are arranged superposed one above another and aredisplaceable from a retracted position in which they do not extend alongthe path of any member carried by the ro tating equipment to a secondwork position. In this work position, which they reach due todisplacement towards the inside of the machine, they control certainmembers of the unit. More precisely, the latches 25 define a pluralityof control means including a first portion 27, and a second portion 26respectively, said second portion forming an extension of the firstportion. The extension 27 of each latch is downwardly inclined from anupper end to a lower end to a level corresponding to that in which thetooth 24 of the slide 20 is carried when the latter engages the loweststep of the cam 18. In the Working position (latch projecting towardsthe inside of the machine) the position of the portion 26 is such as tobe, with a lateral projection thereof, in the path of the step cam 18during its rotational movement fast with the rotating equipment. Inanalogous manner the position of the extension 27 of each latch is suchas to be in the path of the tooth 24. The selection of the latch whichmust be displaced from the rest position to the work position is givenby a suitable control apparatus, not shown, and controlled, for example,by a program tape. Besides said latclies, on the fixed framework of themachine, adjacent the peripherally extending zone thereof in which thesubstitution of one thread guide with another must take place, there isprovided a pair of flat inclined earns 28 and 29 which, in restconditions, do not lie in the path of the members fast with the rotatingequipment but which move, in work conditions, so as to reach the path ofthe lug 11 of the conveyor 10. In such manner the cam 28, the operativeposition of which is shown in FIG. 6, is designed. assuming that therotating equipment moves in anti-clockwise direction, to raise theconveyor which is then re-lowered when the lug or snug 11 slidesdownwards on the cam 29, the operative position of which is shown indotted lines in FIG. 7.

There will now be described in detail a single thread guide 8. Thethread guide 8 is fast with a resilient lamina 30 which is secured atits upper end 31 to the thread guide. Said lamina is normally maintainedresting on the body of the thread guide and acts as a thread brakingpincer designed to retain near its lower end the end of the thread whenit is cut adjacent the end selvage of the fabric. The pincer mustre-open adjacent the front selvage of the fabric in order not toobstruct the free advancement of the thread during the formation of theknitwear. For such purpose rods 32 (equal in number to that of thethread guides) are arranged radially to cross the body of the drum '5 atthe side of each thread guides and to push end-wise against the laminas30. Said rods 32 are arranged, in rest conditions, as illustrated inFIG. 7 by means of compressed springs 33. In this position a respectiveridge 32a of each stem 32 abuts against a plate 32b. The end of the rodrelative to that of the thread guide which is arranged in the workposition (and that is in front of the conveyor 10) is urged by abell-crank lever 34 which is pivotable about its pivot axis 35 whichsecures it to the rotating equipment. Again secured to the rotatingequipment there is provided a fixed sleeve 36 in which a hollow piston37 slides. Between the horizontal arm of the lever 34 and the piston 37there is interposed a spring 38 while on the outside of the piston thereis provided a step 39 designed to co-operate with the tooth 40 whichprojects inwardly from the vertical portion of the lever 34. The levermember 34 can thus pass from the position shown in FIG. 6 to that shownin FIG. 7, which corresponds tothe open and closed positions of thepincers, respectively. In fact, twoseparate control members (not shown)are provided which are designed to act, when a change of thread isrequested, along the arrows F1 "and F2, respectively, on the piston 37so that it slides upwardly and on the base of the lever 34 causing thelatter to move outwards, radially with respect to the machine. Due tothe control along F1 of the piston, the tooth 40 zengages beneath thestep 39 and raises the stem 32 considered into the retracted position,while under the action of the force F2 the tooth 40 frees the step 39and permits the lowering of the piston 37 under the action of the spring38, so that the stern once again projects. Advantageously the lever 34engages the stem 32 by means of a curved profile 34a which is designedto also act as a support surface for the ends of the various rods 32during the rotation of the drum 5.

In this case the actions F1 and F2 cause the simultaneous retraction andprojection of more than one stem 32 but not of all (see FIG. 8), andtherefore the closure and the opening of the corresponding pincers orlaminas 30. The opening occurs to a different extent for each of saidpincers because of the shape of the profile (see FIGS. 2 and 8).Finally, 41 indicates a seal sheath for the thread guides which is fastwith the drum.

The working of the thread guide unit according to the invention is asfollows.

It is supposed that at the end of the formation of a row of theknitting, there is programmed in the machine a change of the threademployed in the formation of the knitting, and, that is, a replacementof the thread guide in operation with another thread guide whichclock-wise follows the former in clock-wise direction along the skirt ofthe drum. In relation to this, from the unit of latches 25 projects thelatch corresponding to the new thread guide to be utilized.

Due to the interrupted rotation of the rotating equipment (which is, asstated, anti-clockwise), the end of the extension 27 is engaged (FIG.14) by the end 24 of the slide 20, which moves along the inclined planeof said extension 27 so that the slide 20 rises to the highest level ofsaid plane. With the progressive raising of the slide 20, and thereforewith the disengagement of the slide 20 from the step which previouslyretained it, the drum is caused by the spring 6a to rotate inanti-clockwise direction until a new step 18 is positioned below the nowraised sh-de 2U. Continuing the raising of the slide 20, the drumcontinues to rotate step-wise until a further rotation of the step camand the drum fast therewith is stopped by the final engagement betweensaid slide and the underlying step (FIGS. 15 and 16). In this positionthe new thread guide is carried exactly adjacent the slide or conveyor10.

There is thereby obtained the passage from one thread guide to theother, the two thread guides following each other in clockwise directionalong the guides of the drum. In the case in which the substitution musttake place between two thread guides which follow each other inanticlockwise direction on the drum (for example starting from theposition of FIGS. 9, 11), the rotation of the corresponding step cam iscaused by a respective latch 25 whose portion 26 extends along the pathof the step cam 18 and engages the step which passes adjacent the lineof action of the latch (FIG. 10) and causes the rotation of the cam inclockwise direction against the action of the spring 6a until, byrotating the mobile equipment, the step passes tangentially out of thezone of engagement with the latch (FIG. 12). correspondingly the slide20 is lowered along the steps under the thrust of the compressed spring23. When said step is no longer pushed by the latch, the tooth of theslide 20 locks the drum in the angular position reached at that moment.

It will be understood that, when the actuation of the thread guidesinvolves different thread guides, as it occurs above with regard toFIGS. 9, l0, 12, the latches involved are different, however, when oneand the same thread guide is involved the actuating latch is always oneand the same. In fact the latch 25 used in the above described case, inwhich the portion 26 engages the steps 19 of the drum 5, is the same asthe latch 25 used in the first case explained previously, in which theportion 27 engages the slide member 20, when the same step 19 has to befinally engaged by the slide member 20. In other words each step 19 (oreach thread guide) has its own latch and the same latch is used bothwhen the drum has to be oscillated in clockwise and anti-clockwisedirection to reach the same final position.

The operation of substitution of the thread guide in the above-describedWork position is preceded by the raising the conveyor, guided by theinclined cam 28, rises and the tooth 12a and ring 13' entrains upwardsthe thread guide which has ceased working. There then takes place theabove-described switching operation, so that the new thread guide isarranged adjacent the conveyor 10, with the respective lug 9 arrangedbelow the extension 12a of the conveyor. At the end of the switching,the snug 11 slides along the downward incline of the cam 29 which pushesthe conveyor 10 and consequently the new thread guide into the workposition. Before these operations there takes place the closure of thelamina 30 of the previously described thread braking pincers. After thesubstitution of the thread guide the lamina 30 is opened and therelative thread is freed.

It should be noted that two conjointly controlled thread guides may bearranged in a single guide 7 of the drum. Moreover, advantageously theangular positions which the drum can assume are one greater than thenumber of thread guides operating; that is to say that a supplementarygroove 41a is provided without a thread guide and, in relation thereto,a supplementary step in the cam 18. This is in order to be able tointerrupt every feeding of thread from the thread guide unit underconsideration, during one or more turns of formation of the knitting.This occurs due to the fact that in front of the slidable conveyor 10there is arranged precisely the groove 410, so that, during the loweringof the conveyor, the tooth 12a slides freely in the groove 41a withoutcausing the lowering of any thread guide (note FIG.

It may also be noted that the presence of the half-ring 13 constitutes asafety measure in case of the accidental lowering of thread guides otherthan those to which the selection controls are automatically imparted.As deducible from the foregoing, an accidentally lowered thread guidewill be raised by the half-ring 13 at the next thread change and beforethe rotation of the drum 5.

We claim:

1. In a circular knitting machine having a fixed framework and arotating equipment, a thread guide unit arranged on said rotatingequipment and comprising a hood member, a drum member oscillatinglysupported by said hood member, spring means provided between said hoodmember and said drum member for subjecting said drum member to a torque,parallel grooves distributed on the lateral surface of said drum memberat least over a sector of said drum member, thread guides slidablymounted inside said grooves, to move from a rest position to a workingposition, a step cam circumscribing the drum for an are at least equalto said sector and defining a plurality of steps at least equal innumber to the number of said grooves, a first and a second guidearranged inside said hood member substantially, parallel to the axis ofoscillation of said drum member, a first and a second slide memberlengthwise movable inside said first and said second guide,respectively, said first slide member having means for engaging aselected thread guide to move it from said rest position into saidworking position and vice versa, and said second slide member havingmeans for engaging said steps of said step cam to lock said drum memberagainst the torque of said spring means, a plurality of superposedcontrol means corresponding in number to the number of said steps ofsaid step cam and having each a working position lying in the path ofsaid step cam and of said second slide member, respectively, to cause arotation displacement of said drum member in the one or the other senseto selectively position a thread guide for activation by said firstslide member, and means arranged in the rotation path of said firstslide member for raising and lowering it in phase relationship with theoperation of said control means.

2. A thread guide unit according to claim 1, wherein each said threadguide comprises an upper end provided with a lug projecting outwardlyand radially to said drum member and wherein said means provided on saidfirst slide member for engaging said thread guides comprises a raisingmember fast with said first slide member and shaped according to an arcof a circle engaging said lug of said thread guide from the bottom, thusraising it from said working position to said rest position, and a snugrigid with said first slide member, mounted over said raising member andspaced therefrom engaging said lug from the top, thus urging saidselected thread guide from the rest position into the working position.

3. A thread guide unit according to claim 1, wherein a supplementaryempty groove is provided on said drum member parallel to said grooves ofsaid drum member; a step being provided on said step cam cooperatingwith said supplementary empty groove for interrupting thread feedingfrom the said thread guide unit of the circular knitting machine.

4. A thread guide unit according to claim 1, further having threadbraking means associated to said thread guides, said thread brakingmeans comprising a plurality of thread braking pincers equal in numberto the number of the thread guides and each formed by a resilient laminawith an upper end secured to the thread guide and a lower end arrangedfree to clamp the thread between the associated thread guide and saidlower end, a plurality of rods mounted on said drum member substantiallytransversely to said laminas and engaging said laminas nearthe lower endthereof, a lever means pivotally mounted'on said hood member, a curvedcam means fast with said lever means for selectively engaging the rodassociated with the selected thread guide, and actuating means for saidlever means causing said cam means to urge said selected rod againstsaid lamina to free the thread'braked by said lamina.

5. A thread guide unit according to claim 1, wherein said plurality ofsuperposed control means comprises a plurality of latches arranged oneover the other and having each an inclined portion extending between alower and an upper end thereof, said lower and said upper ends and saidinclined portion lying in said working position in the path of saidmeans of said second slide member engaging said steps of said step camfor disengaging said second slide member from one of said steps andengaging with another of said steps after a rotation displacement ofsaid drum member due to said spring means.

6. A thread guide unit according to claim 1, wherein said plurality ofsuperposed control means comprises a plurality of latches arranged oneover the other and having each a lateral projection lying in saidworking position in the rotation path of one of said steps of said stepcam, thus causing the engagement of the relative latch .with said stepand a rotation displacement of said drum member against the action ofsaid spring means and locking of said drum member by said second slidemember'in another position.

References Cited UNITED STATES PATENTS 971,986 10/1910 Gee 66l392,961,857 11/1960 Green 66138 X 3,521,466 7/1970 Tannert 6619 FOREIGNPATENTS 402 1876 Great Britain 6 ,6l39

ROBERT R. MACKEY, Primary Examiner U.S. Cl. X.R. 66-139

